1. Field of the Invention
This invention relates to a liquid crystal display, and more particularly to a liquid crystal display and a fabricating method thereof wherein four masks are used so as to reduce a process.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) includes switching devices consisting of thin film transistors having gate electrodes, a gate insulating film, an active layer, an ohmic contact layer and source and drain electrodes, and a liquid crystal injected between a lower plate provided with pixel electrodes and an upper plate provided with color filters.
FIG. 1 is a plan view showing a structure of a conventional LCD, and FIG. 2 is a section view of the conventional LCD taken along the Axe2x80x94Axe2x80x2 line in FIG. 1. Referring to FIG. 1 and FIG. 2, in the conventional LCD, a gate electrode 13 is formed on a transparent substrate 11 from a metal such as aluminum (Al) or copper (Cu) in such a manner to be connected to a gate line 14. A gate insulating film 15 is formed on the transparent substrate 11 to cover the gate electrode 13 and the gate line 14. The gate insulating film is made from silicon nitride or silicon oxide.
An active layer 17 and an ohmic contact layer 19 are provided at a portion corresponding to the gate electrode 13 on the gate insulating film 15. The active layer 17 is formed from amorphous silicon or polycrystalline silicon being not doped with an impurity. The ohmic contact layer 19 is made from amorphous silicon or polycrystalline silicon doped with an n-type or p-type impurity at a high concentration.
Source and drain electrodes 21 and 23 are formed at each side of the active layer 17 on the gate insulating film 15 in such a manner to contact the ohmic contact layer 19. The source and drain electrodes 21 and 23 is made from a metal such as molybdenum (Mo), chrome (Cr), titanium (Ti) or tantalum (Ta), etc., or a molybdenum alloy such as MoW, MoTa or MoNb, etc. The source electrode 21 is connected to a data line 24 while the drain electrode 23 is opposed to the source electrode 21 with having the gate electrode 13 therebetween.
A thin film transistor is constituted by the gate electrode 13, the gate insulating film 15, the active layer 17 and the source and drain electrodes 21 and 23 as described above. A passivation layer 25 is formed on the gate insulating film 15 to cover the thin film transistor. The passivation layer 25 is made from an inorganic insulating material such as silicon nitride or silicon oxide, etc., or an organic insulating material such as acrylic compound, BCB (xcex2-stagged-divinyl-siloxane-benzocyclobutene) or PFCB (perfluorocyclobutane).
A contact hole 27 for exposing the drain electrode 23 is defined at the passivation layer 25. A pixel electrode 29 contacting the drain electrode 23 via the contact hole 27 is formed on the passivation layer 25. The pixel electrode 29 is formed from a transparent conductive material such as indium tin oxide (ITO), tin oxide (TO) or indium zinc oxide (IZO) at an area excluding a portion corresponding to the thin film transistor on the passivation layer 25.
However, the conventional LCD has a problem in that, since a contact hole must be defined so as to connect the drain electrode to the pixel electrode, an aperture ratio is reduced and a process is complicated.
Accordingly, it is an object of the present invention to provide a liquid crystal display and a fabricating method thereof wherein a drain electrode and a pixel electrode are connected to each other with no contact hole, thereby increasing an aperture ratio.
In order to achieve these and other objects of the invention, a liquid crystal display device according to one aspect of the present invention includes a transparent substrate; a gate electrode formed on the transparent substrate; a gate insulating film formed on the transparent substrate to cover the gate electrode; an active layer provided at a portion corresponding to the gate electrode on the gate insulating film; source and drain electrodes intervened by an ohmic contact layer on the active layer; a contact portion connected to and extended from a portion of the drain electrode opposed to the source electrode and having an exposed side surface; a passivation layer formed on the active layer in such a manner to cover the source and drain electrodes, but to expose the side surface of the contact portion; and a pixel electrode formed on the gate insulating film in such a manner to contact the exposed side surface of the contact portion.
A liquid crystal display device according to another aspect of the present invention includes a transparent substrate; a gate electrode formed on the transparent substrate; a gate insulating film formed on the transparent substrate to cover the gate electrode; an active layer provided at a portion corresponding to the gate electrode on the gate insulating film; source and drain electrodes intervened by an ohmic contact layer on the active layer; at least one of come-shaped contact portion connected to and extended from a portion of the drain electrode opposed to the source electrode and having an exposed side surface; a passivation layer formed on the active layer in such a manner to cover the source and drain electrodes and the upper portion of the contact portion, but to expose the side surface of the contact portion; and a pixel electrode formed on the gate insulating film in such a manner to contact the exposed side surface of the contact portion.
A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the steps of forming a gate electrode on a transparent substrate; sequentially forming a gate insulating film, an active layer and an ohmic contact layer on the transparent substrate in such a manner to cover the gate electrode; forming a metal thin film on the ohmic contact layer and then patterning the metal thin film to expose the active layer, thereby forming source and drain electrodes; forming a passivation layer covering the source and drain electrodes on the active layer and then patterning the passivation layer and the active layer to expose the gate insulating film and also a portion of the drain electrode opposed to the source electrode and formed to have more than a desired size, thereby providing a contact portion connected to and extended from the drain electrode to have an exposed side surface; and forming a pixel electrode on the gate insulating film in such a manner to contact the side surface of the contact portion.